Until late 18th century, the forests of the sanctuary were under the control of the of the Nilambar Tirumalapad religious sect (Tirumalapad Kovilagam). In 1927 the area was declared a reserved forest. The park was created in 1940 to become the first wildlife sanctuary in South India. Originally 62 km2 (24 sq mi), the sanctuary was enlarged to 295 km2 (114 sq mi) in 1956. In 1958 the sanctuary was extended to 318.7 km2 (123.1 sq mi) and subsequently to its present size of 321 km2 (124 sq mi). The sanctuary is contiguous with Bandipur National Park (874 km2 (337 sq mi)), Wynad Wildlife Sanctuary (344 km2 (133 sq mi)) and Sigur and Singara reserve forests.

The park is part of the Nilgiri Biosphere Reserve. There are 48 tigers in the Nilgiri Reserve across which tigers are free to roam. In April, 2007, the Tamil Nadu state government declared Mudumalai as a Tiger Reserve, under section 38V of the Wildlife Protection Act of 1972, in an effort to conserve the country's dwindling Tiger populations. Subsequently, about 350 families living in the core area have been evicted from the park and given 1 million rupee ($20,800) compensation. Those in the 5 km buffer area around the park fear they too will be evicted, however, nobody will be dislodged from the buffer zone. In fact, some people in this zone will be involved in the project as trackers and guides to enhance their income through eco-tourism.
View of the forest
Working elephant near bamboo thicket at Moyer River

There are three main types of forest in the sanctuary: tropical moist deciduous occur in the western Benne Block, where rainfall is higher than in the other blocks. Tropical dry deciduous forest occurs in the middle and southern tropical dry thorn forests are in the east.

In addition there are patches of tropical semi ever green forest in the Southwest and Western part of Mudumalai. The annual rainfall there exceeds 2,000 mm (79 in). Tree species in this habitat include: Casseria ovoides, Litsea mysorensis, Cinnamomum malabatrum and Olea dioca. Climbers, including: Todalia asiatica, Sneeze Wort (Watakaka volubilis), Gnetum ula and Entada scandens are also found in these semi evergreen forests.

Moist Bamboo brakes are found amidst dry deciduous, moist deciduous and semi-evergreen forests and along the fringes of riparian forests and swamps. There are two species of bamboo found in Mudumalai, the giant clumping bamboos: Bambusa (arundinacea) and Dendrocalamus strictus. Elephants and Gaur eat both species of bamboo.

In all types of forest, a green strip of riparian forest is seen along the shore of dry seasonal and perennial streams. This type of forest remains green in all seasons. The plant species found here includes: Mangifera indica, Pongamia glabra, Terminalia arjuna, Syzygium cumini, Indian rosewood Dalbergia latifolia and the bamboos. Larger mammals such as elephant, gaur, sambar and tiger use riparian forest patches for feeding and resting.

This sanctuary is home to several species of wild relatives of cultivated plants including wild rice, wild ginger, turmeric, Cinnamon, Solanum, Guava, mango and pepper that act as a reserve gene pool for the cultivated plants.

In certain places mixed vegetation types are present. The deciduous trees shed their green leaves during the summer, and adopt a floral garb while the arrival of the monsoons hails fruits and tender greens.